Reciprocating carriage for electrographic printing

ABSTRACT

Printing apparatus employing a pair of reciprocating print heads, one of which traverses the entire print field in a record mode while the other one moves in the opposite direction in an inoperative mode. The print heads are supported for movement on separate, spaced apart guide rails such that the pens thereof print along the same line relative to a moving recording web. To this end, structure is provided for causing movement of the nonprinting pen out of the path of travel of the other pen as well as disengagement from the recording medium.

United States Patent Brock 1 June 27, 1972 [54] RECIPROCATING CARRIAGE FOR ELECTROGRAPHIC PRINTING [72] Inventor: John L. Brock, Thruway Homes, N.Y. [73] Assignee: Xerox Corporation, Stamford, Conn.

22 Filed: June is, 1970 21 Appl. NOJ 46,674

52 us. 01. 6346/1319 R, 346/74 ES 51 1 1111. C1. ..G0ld 15/24 [58] Field of Search ..346/l39 R, 49, 74 ES; 178/66,

[56] References Cited UNITED STATES PATENTS 2,311,803 2 1943 Wise et a1. ..178/6.6 2,587,145 2/1952 Grib ..346/l39X 2,622,001 12/1952 Cooley ..346/l39 3,518,699 6/1970 Mitchell ..346/74 Primary Examiner-Joseph W. Hartary Attorney.iames J. Ralabate, John E. Beck and Benjamin B. Sklar [57] ABSTRACT Printing apparatus employing a pair of reciprocating print heads, one of which traverses the entire print field in a record mode while the other one moves in the opposite direction in an inoperative mode. The print heads are supported for movement on separate, spaced apart guide rails such that the pens thereof print along the same line relative to a moving recording web. To this end, structure is provided for causing movement of the non-printing pen out of the path of travel of the other pen as well as disengagement from the recording medi- 13 China, 5 Drawing Figures PHENTEDJUNZY 1972 I SHEET 10F 3 fllrlnll'llliflvlliillilollll v INVENTOR. JOHN L. BROCK FIG. 1

RECIPROCATING CARRIAGE FOR ELECTROGRAPHIC PRINTING BACKGROUND OF THE INVENTION would print or record during movement, for example, from left to right across the recording medium and then be rapidly returned to the left endof the recording medium to start printing another line of information. During this return movement of carriage return, no recording takes place, therefore, such movement commonly referred to as dead-time" adversely effects the overall speed and operation of the apparatus.

Attempts at designing a system with faster carriage return capabilities have fallen short of producing a totally satisfactory apparatus. This led tothe development of systems employing multiple print heads for minimizing the dead-time." One such system utilizes two print heads which are reciprocated along the same line. During one cycle of operation the heads are moved toward and then away from each other, one head printing while the other one is tumed off.

While such aprint head arrangement minimizes the "deadtime" due to carriage return, it imposes certain restrictions on other partsv of the system. For example, it necessitates the utilization of complicated and expensive signal generating and logic circuitry for controlling the printheads. This is because each print head must be turned off during turn around which occurs twice during each cycle for each print head. Furthermore,-since the print heads are in continuous contact with the recording medium, each head must be turned off during half its path of travel as well as during turn around. Continuous contact. with the recording medium also produces excessive wear of the styli.

Accordingly, the general object of this invention is to pro vide a new and improved printing apparatus. 7

.It is a more particular object of this invention to provide, in a printing apparatus, new and improved electrorecording structure.

Another. object of this invention is to provide in printing apparatus, electrorecording structure, which makes it possible to build an apparatus which is less expensive, more efficient and less complex in construction.

BRIEF SUMMARY OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of a printing apparatus comprising a pairof print heads which are reciprocally mounted on separate guide rails. The print heads are reciprocated in opposite directions and are so arranged that one head is moving from left to right and is in a print or record mode while the other head is moving in a direction from right to left and is inoperative. In other words as one head traverses the recording medium in the record mode the other head is movingtowards its start of record positron.

Each of the print heads is retractable from engagement with the recording medium as well as movable out of the path of movement of the other recording or print head. At least two advantages are obtained from the foregoing, therefore, complicated signal generating and logic circuitry is unnecessary since continuous data can be transmitted to both ends and the heads can record along the same line relative to a moving recording web. The effect of the latter is to permit continuous movement of recording material. Y

A cam and follower arrangement is provided for each print head which causes head retraction and movement out of the path of travel of the other head. When the cam and follower arrangement is inoperative the styli of the recording print head are spring biased into engagement with the recording medium. Consequently, as the styli wear the spring force maintains constant pressure of the styli against the recording medium.

Further objects and advantages of the present invention will I become more apparent when considered in view of the detailed description of the preferred embodiment of the invention and drawings forming a part hereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevational view of the printing apparatus representing the invention;

FIG. 2'is a perspective illustration of the printing station, as viewed from the bottom, of the apparatus shown in FIG. 1;

FIG. 3 is a perspective view of a print head assembly;

FIG. 4 is a schematic representation of the path of travel of a pair of print heads incorporated in the apparatus of FIG. I; and

FIG. 5 is a cross-sectional view taken on the line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, especially FIG. 1, reference character 10 designates generally a recording or printing apparatus comprising housing structure 12 including a transparent viewing window 14 through which printed messages can be read during operation of the apparatus.

The messages or information are printed upon a recording web 16 which is moved from a supply reel 18 located adjacent the lower portion of the housing structure 12. A pair of motor driven feed rollers 20 and 22 which grip the paper serve to transport the paper past a recording station 24, a developer station 26 and a fusing station 28.

A pair of print head assemblies generally indicated 30 and 32 are supported for reciprocatory movement at the recording station transversely of the apparatus (see FIG. 2) by apair of support or guide rails 34 and 36. The assemblies 30 and 32 constitute an electrographic recording arrangement forming an important part of the invention. In the electrographic recording process, indicia to be printed, such as letters,'lines, dots, pictures, etc. are first formed as invisible 'orlatent electrostatically charged surface areas of a charge-retentive recording medium such as the web I6by means of voltages impressed thereon by suitably positioned electrodes. Subsequently, these charged areas are developed or rendered visible by the application off'mely divided pigmented powder, to the surface of the recording medium, as a developing agent or "ink," the powder being held to the medium by electrostatic attraction in the charged areas. Liquid inks could also be employed. In the apparatus disclosed, the aforementioned development is accomplished at the developer station 26 by means of a fiber brush 38 which is rotated in the counterclockwise direction, as viewed in FIG. 1, such that the extremities thereof contact the web 16. Toner material 40 disposed in a sump area 42 is presented to the brush 38 by means of a donor device 44 also rotated in the counterclockwise direction as viewed in F IG. 1.

In this type of development system, the fiber brush is constructed in the form of a cylinder mounted for rotation on a shaft 45. The fibers, through triboelectric action, attract the toner material thereto and thus hold the toner until it is presented to the electrostatic image on the recording web. As the fibers contact the recording web they become somewhat flexed due to the spacing of the brush relative to the web.

' When the fibers straighten out a flicking action occurs which sistance element 48 provides means for rendering the developed image permanent. Other techniques known in the electrographic as well as the xerographic arts may also be utilized, for example, subjecting the developed image to a solvent vapor or spraying the image with an overcoating.

After fusing, the finished recording is moved through a transverse opening 50 in the top wall of the housing structure 12. A tear strip or bar 52 at the opening 50 may be provided for tearing a portion of the web containing a recorded message from the web, as desired by the user.

While an electrographic recording arrangement is disclosed it will become apparent hereinafter that the inventive concept lends itself to other types of recording, for example, electrolytic or electrochemical.

As viewed in FIGS. 1 and 2, the guide rails 34 and 36 are disposed in a horizontal plane subadjacent the web 16 such that the head assemblies carried thereby can be reciprocated transversely of the web in opposite directions. Movement of the assemblies is accomplished by means of a cable 52 attached thereto in a manner to be described hereinafter. A reversible DC motor 54 having a pulley 56 secured to an output shaft 58 thereof imparts reciprocating movement to the cable 52 which, in turn, imparts such motion to the print head assemblies 30 and 32. Motor reversing can be obtained by the provision of a pair of variable position sensors or switchers (not shown) which are set at desired positions along and adjacent to the guide rails 34 and 36. The exact positioning of the sensors depends on the desired format on the recording medium. In other words, if it were desired to print across the entire width of the paper, the sensors or switches would be located at the edges of the web 16. This would result in full width printing.

The assembly 32, as best illustrated in FIG. 3, comprises a carriage structure 59 including a base member 60 which encompasses the guide rail 36 and through a plurality of bearing structures 62 and 64 carried internally of a longitudinal bore 66 thereof rides on the guide rail 36.

A rod 65 carried by the base member 60 pivotally supports a frame member 68 which, as viewed from the top in FIG. 3,

has a generally I-I-shaped configuration. The frame member I pivots about a generally horizontal axis and carries a pen holder 70 which is supported for pivotable movement about a generally horizontal axis by means of a pivot shaft 72.

The pen holder 70 has attached thereto, by means of a single fastener, herein disclosed as a screw 74, and electrorecording pen 74. The pen 74 comprises a plurality of styli 78 arranged in a row which extends along the longitudinal axis of the web. In other words, the row of styli is perpendicular to the transverse dimension of the web. A set of input leads 80 having a lead for each styli is attached to a connector (not shown) to which a second set of input leads (not shown) for the assembly 30 is attached. Each set of leads receives, from a signal generating structure, for example, a digital computer, the exact same signals. The sets of leads are hard wired both to the pens and the connector and are sufficiently long so as to permit full page recording by the recording pens and render unnecessary, complicated commutating systems.

The styli 78 physically contact the web 16 which passes over a backing electrode 81 disposed on the side of the web opposite from the styli. With this arrangement, printing of an electrostatic image on the web occurs when a suitable difference of potential, for example, 750 volts, is exhibited between the styli and the backing electrode, which together forms mutually insulated and spaced apart electrode means. As the styli move across the web, suitable pulsing and pen selection circuitry (not shown) applies short electrical pulses to selected styli in accordance with transmitted information. In this manner an entire line of latent electrostatic images is formed and ready for development.

In its operational or recording mode as illustrated in FIG. 3, the pen 76 is being moved by the cable 52 in a direction that is into the paper. When viewed from the top or front of the apparatus, movement is from left to right during recording and in the reverse direction during non-recording. The assemblies 30 and 32 are attached to the cable 52 such that they move in opposite directions and are transversely spaced so that one is at the left side of the web in a position to start printing the other assembly is at the right edge of the web in its position to stop printing. To this end, the cable 52 extends through an aperture 82 in a cylindrically-shaped rock arm or cam 84 and is secured thereto by means of a set screw 86, see FIGS. 3 and 5.

An end 88 of the cam 84 engages a cam follower 90 forming an integral part of the frame member 68. The cam 84 which can be moved across an inclined surface 92 of the cam 84 by means of the cable 52, in so doing, has the effect of pivoting the frame member 68 against the bias of a pair of springs 94 attached at one end to the frame member 68 and at the other to the base member 60 while being wrapped around the rod 66 about which the frame member 68 pivots. The pivoting of the frame member 68 is in the counterclockwise direction as viewed in FIG. 3. As the frame member is so moved, the rear edge 96 of the pen holder 70 adjacent the top thereof engages an adjustable stop member 98 carried by one arm of the base member 60. Such engagement coupled with further movement of the frame member 68 causes clockwise pivoting of the pen holder 70 and therefore, the pen 76 about the shaft 72, in opposition to the bias of a pair of springs 100 (only one being shown). The springs 100 are attached at one end to a stud 102 integral with the holder 70 and at its other end to the frame member 68 as indicated at 104. The foregoing arrangement accomplishes two things, first, it effects pen retraction from the recording medium and, second, it moves the pen to a position which prevents interference with the movement of the other print head assembly. In order that the styli squarely contact the paper along their lateral extent, each pen and its associated styli have a curvilinear configuration compatible with the two directional movement of the pins, as hereinabove described.

The rocker arm or cam 84, as viewed in FIG. 5, is pivotally attached to the base member 60 by means of a yoke 106 and a rod 108, the latter of which extends through a leg 110 of the base member 60. In order to maintain the pen in the retracted position, a notch 112 (FIG. 3) is provided in the cam follower 90 which holds the rocker arm in the pen retracting position while the print assembly moves from left to right in the machine. Movement of the rocker arm into and out of the notch is accomplished as a result of the cable force opposing the carriage inertia when the motor 54 reverses.

The assembly 30 is identical to the assembly 32 except for its pen 70 and cam follower 90 which are mirror images of the pen 70 and the follower 90 so that the assemblies are operationally compatible. That is to say, that since the assemblies move in opposite directions and since one pen is in the recording position while the other is retracted, the interaction of the cam and cam follower of one assembly must give the opposite result of the other assembly at any given moment. While one assembly, for example, the assembly 32, is in the recording mode as viewed in FIG. 3 and 4 the relationship of the cam 84 to the cam follower 90 is as illustrated. At this time, the cam 84 and cam follower 90 are such as to have the end 88 disposed in its associated notch. This results, as illustrated schematically (see FIGS. 1 and especially the latter FIG.) in the pen 70 moving along a print path 120, in a left to right direction while the pen 70' is offset therefrom while moving in the reverse direction. This situation is reversed when assembly 30 moves from left to right and the assembly 32 is moving in the opposite direction. It can be seen from FIG. 4 that the pens 70 and 70' print along the same path, therefore path 120. For this reason the movement the paper can be continuous therefore resulting in a simple motor and drive arrangement therefor.

Since the assemblies 30 and 32 unlike prior art constructions, are each supported by a single guide rail, a support structure generally indicated 122 is provided in order to remain parallelism thereof relative to the recording medium. The structure 122 comprises the guide rails 34 and 36 which are hexagonal in cross-section. The structure 122 further comprises bearing structures 62 and 64, the former of which are rigidly supported within the base member 60 and the latter of which are movably supported therein to allow for wear. While various means for movably supporting the bearing structure 64, of which there are two (one at each end of the base member), a pair of resilient members 126, (only one being shown) are compressed by set screws 128 against a bearing shaft 130, the shaft being'eccentric with respect to the bearing structures 64. As can be seen the sides of the guide rail are of unequal length, therefore, the sides contacted by the bearing structures are longer than the sides not contacted by the bearing structures. This configuration yields greater bearing surface than other possible configurations. The particular configuration will be dictated to a large degree by the operation desired and product cost limitations.

What is claimed is:

1. Print head structure comprising:

a base member adapted for reciprocating movement on a guide rail;

a first member pivotably supported on said base member;

a second member pivotably supported by said first member;

a recording pen carried by said second member;

means carried by said base member cooperating with said second member in response to pivoting of said first member to cause pivoting of said pen into an inoperative position;

cam structure pivotably secured to said base member;

said second member comprising a cam follower cooperating with said cam structure to effect pivoting of said first member when said cam is acted on by a force external to said print head structure;

spring means for urging said members in directions opposite to that caused by the interaction of said cam and cam follower to thereby maintain said cam in a recording position when said cam and'cam follower are not interacting.

2. Printing head structure comprising:

a base member;

a carriage member pivotably supported by said base member;

a recording pen;

means for pivotably attaching said pen to said carriage;

means carried by said base member cooperating with said last-mentioned means to cause pivoting thereof when said carriage member is pivoted, and;

means carried by said base member for effecting movement of said carriage member.

3. Structure according to claim 2 including means for normally urging said carriage member and said pen-attaching means in directions opposing the directions of motion imparted by said means carried by said base member.

4. Structure as best described in claim 3 wherein,

each print head structure comprises,

a base member encompassing one of said spaced apart means;

a frame member pivotably supported by said base member;

and

a pen holder pivotably carried by said frame member, and;

means integral with said base member cooperating with said holder to effect pivoting thereof upon pivoting of said frame member.

5. Electrographic printing apparatus comprising:

means for moving a recording web sequentially past a recording station, developing station and a fusing station;

at least one print head structure including a pen having a plurality of styli;

a pen holder;

a frame member supporting said pen holder;

a base member pivotally supporting said frame member;

means supporting at least one print head structure for reciprocating movement transverse of said web;

a motor;

a rocker arm movably carried by said base member for movement therewith and engaging said frame member for effecting pivoting thereof; and

means coup mg said rocker am and said motor, said rocker arm being actuatable by said motor and said coupling means.

6. Structure as specified in claim 5, including means for pivotally mounting said pen holder to said frame member and means carried by said base member for causing pivoting of said pen holder in response to pivoting of said frame member.

7. Structure as specified in claim 5 including means for .pivotally mounting said pen holder to said frame member for movement in a first direction when said frame member pivots, pivoting of said frame member being in a different direction from said first direction; and

means for effecting pivoting of said pen holder when the frame member is pivoted.

8. Printing apparatus comprising:

means for moving a recording web past a recording station;

a pair of printhead structures including recording pens;

spaced apart means supporting said printhead structures for reciprocating movement transverse of said web;

a reversible motor;

means for positioning one of said pens out of contact with said recording medium and out of the path of travel of the other printhead structure;

means for simulteneously positioning the other of said pens in contact with said recording medium;

means supported by said printhead structures coupled to said reversible motor for simultaneously moving said printhead structures in opposite directions across substantially the full width of said recording medium and for actuating said positioning means.

9. Structure as described in claim 8 wherein, each printing head structure comprises:

a base member encompassing one of said spaced apart means;

a frame member pivotably supported by said base member;

a pen holder pivotably carried by said frame member, and;

means integral with said base member cooperating with said holder to effect pivoting thereof upon pivoting of said frame member.

10. Structure as specified in claim 9 wherein, said means for positioning said other of said pens in contact with said recording medium comprises a plurality of bias springs normally urging said frame member and said pen holder in opposition to the direction of movement caused by said means for positioning said one of said pens out of contact from said recording medium.

11. Structure as specified in claim 10 wherein, said means supported by each printhead structure comprises a rocker arm and a cable attached thereto, said rocker arm serving to cam said frame member to effect pivoting thereof.

12. Structure as specified in claim 9, including bearing structure disposed in said base member, and wherein said printhead supporting means comprises a guide rail having a hexagonal shape in cross section, said bearing structure including members in engagement with three sides of said guide rail thereby constituting a three-point suspension arrangement for maintaining parallelism between the printhead structure and the recording medium.

13. Structure as specified in claim 12, including means for compensating for bearing and support wear. 

1. Print head structure comprising: a base member adapted for reciprocating movement on a guide rail; a first member pivotably supported on said base member; a second member pivotably supported by said first member; a recording pen carried by said second member; means carried by said base member cooperating with said second member in response to pivoting of said first member to cause pivoting of said pen into an inoperative position; cam structure pivotably secured to said base member; said second member comprising a cam follower cooperating with said cam structure to effect pivoting of said first member when said cam is acted on by a force external to said print head structure; spring means for urging said members in directions opposite to that caused by the interaction of said cam and cam follower to thereby maintain said cam in a recording position when said cam and cam follower are not interacting.
 2. Printing head structure comprising: a base member; a carriage member pivotably supported by said base member; a recording pen; means for pivotably attaching said pen to said carriage; means carried by said base member cooperating with said last-mentioned means to cause pivoting thereof when said carriage member is pivoted, and; means carried by said base member for effecting movement of said carriage member.
 3. Structure according to claim 2 including means for normally urging said carriage member and said pen-attaching means in directions opposing the directiOns of motion imparted by said means carried by said base member.
 4. Structure as best described in claim 3 wherein, each print head structure comprises, a base member encompassing one of said spaced apart means; a frame member pivotably supported by said base member; and a pen holder pivotably carried by said frame member, and; means integral with said base member cooperating with said holder to effect pivoting thereof upon pivoting of said frame member.
 5. Electrographic printing apparatus comprising: means for moving a recording web sequentially past a recording station, developing station and a fusing station; at least one print head structure including a pen having a plurality of styli; a pen holder; a frame member supporting said pen holder; a base member pivotally supporting said frame member; means supporting at least one print head structure for reciprocating movement transverse of said web; a motor; a rocker arm movably carried by said base member for movement therewith and engaging said frame member for effecting pivoting thereof; and means coupling said rocker arm and said motor, said rocker arm being actuatable by said motor and said coupling means.
 6. Structure as specified in claim 5, including means for pivotally mounting said pen holder to said frame member and means carried by said base member for causing pivoting of said pen holder in response to pivoting of said frame member.
 7. Structure as specified in claim 5 including means for pivotally mounting said pen holder to said frame member for movement in a first direction when said frame member pivots, pivoting of said frame member being in a different direction from said first direction; and means for effecting pivoting of said pen holder when the frame member is pivoted.
 8. Printing apparatus comprising: means for moving a recording web past a recording station; a pair of printhead structures including recording pens; spaced apart means supporting said printhead structures for reciprocating movement transverse of said web; a reversible motor; means for positioning one of said pens out of contact with said recording medium and out of the path of travel of the other printhead structure; means for simulteneously positioning the other of said pens in contact with said recording medium; means supported by said printhead structures coupled to said reversible motor for simultaneously moving said printhead structures in opposite directions across substantially the full width of said recording medium and for actuating said positioning means.
 9. Structure as described in claim 8 wherein, each printing head structure comprises: a base member encompassing one of said spaced apart means; a frame member pivotably supported by said base member; a pen holder pivotably carried by said frame member, and; means integral with said base member cooperating with said holder to effect pivoting thereof upon pivoting of said frame member.
 10. Structure as specified in claim 9 wherein, said means for positioning said other of said pens in contact with said recording medium comprises a plurality of bias springs normally urging said frame member and said pen holder in opposition to the direction of movement caused by said means for positioning said one of said pens out of contact from said recording medium.
 11. Structure as specified in claim 10 wherein, said means supported by each printhead structure comprises a rocker arm and a cable attached thereto, said rocker arm serving to cam said frame member to effect pivoting thereof.
 12. Structure as specified in claim 9, including bearing structure disposed in said base member, and wherein said printhead supporting means comprises a guide rail having a hexagonal shape in cross section, said bearing structure including members in engagement with three sides of said guide rail thereby constituting a three-point suspension arranGement for maintaining parallelism between the printhead structure and the recording medium.
 13. Structure as specified in claim 12, including means for compensating for bearing and support wear. 